sql - SQL合并与空字符串

Question

我有以下内容：

Select Coalesce(Other,Industry) Ind from registration

问题是它Other可以是一个空字符串或NULL. 我如何开始coalesce工作，如果Other是一个空字符串，Coalesce仍然返回Industry？

score 189 · Accepted Answer

189

使用CASE表达式或NULLIF：

SELECT COALESCE(NULLIF(Other,''),Industry) Ind FROM registration

于 2013-06-24T19:58:52.237 回答

score 28 · Accepted Answer

28

试试这个

Select Coalesce(nullif(Other,''),Industry) Ind from registration

于 2013-06-24T19:58:58.347 回答

score 5 · Accepted Answer

NULL <> ''您也可以使用不会评估为TRUE...的捷径知道

CASE WHEN other <> '' THEN other ELSE industry END

然后逻辑如下...

CASE WHEN 'fubar' <> '' THEN other ELSE industry END
=> CASE WHEN true THEN other ELSE industry END
=>other
CASE WHEN '' <> '' THEN other ELSE industry END
=> CASE WHEN false THEN other ELSE industry END
=>industry
CASE WHEN NULL <> '' THEN other ELSE industry END
=> CASE WHEN NULL THEN other ELSE industry END
=>industry

3 回答 3